Hydrogen is drawing attention as a clean energy source that does not generate carbon dioxide even when burnt. In order to utilize hydrogen as a fuel, a method of storing and transporting hydrogen has been investigated. As the method of storing and transporting hydrogen, a method involving using a high-pressure gas cylinder is generally used. However, the gas cylinder is heavy. In addition, storage efficiency per unit volume of the gas cylinder has a practical limit, and a significant increase in storage efficiency cannot be expected.
As a hydrogen storage method that replaces the gas cylinder, various materials have heretofore been investigated for hydrogen storage. For example, a method involving utilizing a hydrogen storage alloy has been known. However, the hydrogen storage alloy has a drawback in that the hydrogen storage alloy itself is heavy, and requires heat for releasing hydrogen. For these and other reasons, the range of application of the hydrogen storage alloy is limited. Therefore, there is a demand for development of a material that is more lightweight than the hydrogen storage alloy and that has high hydrogen storage capacity.
In this regard, Patent Literature 1 discloses a porous carbon material in which a volume of pores each having a diameter of 1 nm or less is more than 0.2 cm3/g, and in which a ratio of the volume of the pores each having a diameter of 1 nm or less to a total pore volume is 85% or more.